Sanding machine



Dec. 10, 1957 P. R. VAN SITTERT SANDING MACHINE 3 Sheets-Sheet 1 FiledMay 1, 1957 INVENTOR.

PAUL R. VAN S/TTERT BY M ss 65 I III Fig.5

Dec. 10, 1957 P. R. VAN SITTERT 2,815,613

SANDING MACHINE Filed May 1, 1957 3 Sheets-Sheet 2 7 v 57 INVENTOR.

32 iug R. VAN SITTERT Fig. 7 w \Lm can IN VENTOR. PAUL R. VAN SITTERT 3Sheets-Sheet 3 SANDING MACHINE P. R. VAN SITTERT Dec. 10, 1957 Filed May1, 1957 United States Patent SANDING MACHINE Paul R. Van Sittert,Cleveland, Ohio, ass'ignor to The Rotor Tool Company, a corporation ofOhio Application May 1, 1957, Serial No. 656,367 8 Claims. (Cl. 51-135)The invention relates in general to sanding machines and moreparticularly to sanding machines which are supported at a work area andwhich may be moved angularly in a plurality of planes with respect to asupporting mechanism.

In the automobile industry, as in many others, sanding operations arenecessary. It is quite convenient in many instances to support thesanding mechanism from an overhead position by means of a verticallyextending chain or the like. The source of power for the sandingmechanism also conveniently extends from the overhead position. Sincemany different types of surfaces and objects must be sanded, whichsurfaces and objects may be at any angle with respect to the horizontal,the sander must be moved to accomplish this end. In present sanders,this can be accomplished only by physically lifting and twisting thesanders to meet some positions or by twisting the sander in otherdirections to meet other the support and power lines.

Pulleys are also utilized to support and rotate sanding belts carried bythe sanding machines which accomplish the sanding operation. When asanding belt is new and unused it will tend to locate itselfsubstantially centrally with respect to the pulleys upon which it isturning. When the sanding belt becomes worn and uneven from use, it willno longer locate itself centrally with respect to the pulley but willtend to run oil of the same;

It is therefore an object of the present invention to provide a sanderwhich is capable of many angular movements relative to the vertical andhorizontal, without undue effort and without fouling support and/orpower lines.

Another object of the invention is to provide asander ing belt to trackon a different portion of a pulley of the sander. t

Another object of the invention is to provide a sander having an airmotor mounted on .a support which motor drives a pulley which in turnmoves .a sanding belt, with means for angularl-y adjusting the motor and.hence the pulley to provide a tracking adjustment for the sanding belt.

Other objects and .a [fuller understanding of :my :invention may be hadby referring to the following description and claims, taken conjunctionwith the accompanying drawing, in which:

Figure l is a plan view-of the sanding machine of the present inventionpartially insertion;

positions and fouling Figure 2 is a view taken generally along the line2-2 of Figure '1;

Figure 3 is an end view taken generally along the line 3-3 of Figure 2with the full line drawing illustrating one position of the sander andwith the dot-dash line drawing indicating another position of thesander;

Figure 4 is a view taken along the line 44 of Figure 1 Figure 5 is afragmentary view in section taken generally along the line 5-5 of Figure1;

Figure 6 is a view taken along the line 6-6 of Figure 2;

Figure 7 is a fragmentary view taken generally along the line 7--7 ofFigure 6 and showing the elements of Figure 6 in a different positionrelative to each other; and

Figure 8 is a view taken along the line 8--8 of Figure 3.

The sanding machine of the present invention has been indicatedgenerally by the reference numeral 10 and includes generally a supportmember 12, first and second air motor assemblies 14 and 15,respectively, and a supporting or balancing assembly 16.

The support member 12 may sometimes be referred to as a manifold orcylindrical member and is of a hollow construction and is provided withfirst and second end portions 18 and 19, respectively, and anintermediate portion 20. The supporting or balancing assembly 16comprises a housing 23 which surround the intermediate portion 20 of thehollow cylindrical support member 12. A plate 25 is fixedly secured tothe housing 23 by means of bolts 26 and has an opening 27 through whicha supporting ring 28 extends. A snap 29 (Figure 3) connects with thering 28 and is in turn secured to an overhead support which is not shownin the accompanying drawings. This type of construction supports thesanding machine from an overhead beam or other suitable support.

First and second lock collars 32 and 33, respectively, are fixedlysecured to the cylindrical support member 12 by means of bolts 34 and 35and are located on either side of, the housing 23. This prevents axialmovement of the supporting assembly 16 on the cylindrical member 12 andat the same time permits rotative movement of the cylindrical memberwithin the housing 23. Shoulders 37 are provided on each of the lockcollars and complementary shoulders 38 are provided on the housing 23.These shoulders permit only a predetermined rotational movement of thecylindrical member relative to the housing 23. This movement isapproximately ninety degrees for the machine shown (see Figure 6).

Wall means 41 within the housing 23 define an annular chamber 42 betweenthe housing 23 and the intermediate portion 20 of the cylindricalmember. Openlugs 43 and 44 provide communication between the inside ofthe member 12 and the annular chamber 42. Grooves 45 are provided in thehousing within which reside O-rings 46 which provide an air-tight sealbetween the mating surfaces of the housing and the cylindrical supportmember 12. The housing 23 has a nipple 49 (Figure 6) which is formedintegrally therewith which supportmember 12 and which has an opening 51extending to and communicating with the annular chamber 42.

A swivel member 53 having a bore extending therethrough fits over thenipple 49 and is adapted to rotate thereabout in a plane generallynormal to the extent of the nipple, A bolt 54 screws into the end of thenipple 4? and the head thereof shoulders up against the swivel member 53to maintain the same on the nipple member. The bolt 54 also serves toclose the end of the opening 51 .in. the nipple member. Grooves 57 areprovided in the swivel member within which reside .O-rings 58 whichprovide a rotating seal between the nipple and the swivel member. Theswivel member has an opening 60 which extends generally normal .to theextent of the opening 51 and which communicates with the opening 51,. A

fitting assembly indicated generally at 61 provides for connectionbetween the swivel member 53 and an air supply line 63. This assembly 61may, if desired, be capable of relative rotative movement. Figure 7shows the relative angular movement which is possible because of theconstruction between the swivel member 53 and the nipple 49. With thisconstruction, the cylindrical support member 12 can be moved in a firstplane relative to the air supply line without twisting and fouling theair supply line.

The first and second air motor assemblies each comprise a split collar65 which surrounds the respective end portion of the cylindrical supportmember, which collars are fixedly secured thereto by means of screws 67which extend through the collars and into the cylindrical member. Thecollars are additionally secured to the cylindrical support member bymeans of screws 68 which extend between the ends of the split collar andsecurely bring the two together to tighten the collar about thecylindrical support member. Wall means 70 (Figure 3) are provided ineach of the split mounting collars 65 which define annular chambers 72between the collars and the rmpective end portions of the cylindricalsupport members. Each of the end portions of the cylindrical supportmembers are provided with openings 75 which provide for communicationbetween the cylindrical member and the annular chamber 72. Each of thesplit mounting collars 65 are provided with flanges 77 thereon and theflange of the first air motor assembly has been provided with ordinarycircular openings 79 extending therethrough. A first air motor 80 issecured to the split mounting collar of the first motor assembly 14 bymeans of bolts 82 extending through the openings 79 in the flange of thefirst air motor assembly and into the air motor. Passageway means havebeen provided to admit air into the air motor 80 from the annularchamber 72 of the first air motor assembly. This passageway has not beenshown in the accompanying drawings for the first air motor assembly butit has been shown in the hereinafter second air motor assembly (Figure3) and the two are of a similar construction. The first air motor 80includes a pulley 84 driven by a shaft (not shown) and is adapted tocarry and drive a sanding belt 86 which extends therearound. To providefor good frictional driving engagement between the pulley and thesanding belt, the outside surface of the pulley is preferably made ofrubber or some other suitable frictional material. Integrally formedwith the split mounting collar 65 of the first air motor assembly is anoperating handle 88. The handle 88 is generally opposite the air motor80 with respect to the split mounting collar and extends in generallythe same direction. A first guard supporting post 90 is fixedly securedto the split collar 65 as at 92 (Figure and extends therefrom generallyparallel to the air motor 80. A first sleeve 94 surrounds the guardsupporting post 90 and is capable of rotational movement thereabout. Asecond sleeve 95 surrounds the first sleeve 94 and forms a space orchamber 97 therebetween. An idler plate 99 is carried by the firstsleeve 94 upon which is journalled an idler wheel 100. Extending fromand secured to the second sleeve 95 is a handle 102 secured thereto bymeans of bolts 103. Within the chamber 97 is a spring member 105 havingone end 106 secured to the second sleeve 95 and having the other end 107(Figure 2) secured to the idler plate 99. It will thus be seen thatmovement between the handle 102 and the idler plate 99 is transmitted byway of the spring member 105. The handle or lever arm 102 is movablebetween first and second positions as best seen in Figure 2. The fullline drawing of the handle 102 in Figure 2 shows the handle in the firstposition whereas the dotdash line position 108 indicate the handle asbeing in the second position. A detent 110 is carried by the operatinghandle 88 and is biased upwardly by a spring 111. This spring biaseddetent 110 maintains the handle 102 in the first position. When it isdesired that the handle be moved to the second position, the detent isdepressed and then the handle is capable "of being moved arcuately withrespect thereto which in turn moves the first and second sleeves and theidler plate 99. When the handle 102 is in the first position, the springmember urges the idler plate with a generally constant force in thedirection indicated by the arrow 112 in Figure 2. This maintains asubstantially constant force on the sanding belt 86 which extends aroundand is tensioned by the idler wheel 100.

The idler wheel 100, best seen in Figures 1 and 4, is secured to theidler plate by means of a central bolt or shaft 113 secured in place bya nut 114. The idler wheel 100 is adapted to rotate about this shaft onbearings 118. A one piece U-shaped washer 115 has been provided and isutilized for the purpose of changing or shifting the axis. of rotationof the idler wheel 100. As best seen in Figure 4, the U-shaped washer115 includes first and second opposed wedge shaped sides 116 and 117,respectively.. The side 116 engages and resides on the upper surface ofthe idler plate and the wedge shaped side 117 engages and resides on thelower side of the idler plate. When the nut 114 is tightened with theU-shaped washer in one: position, the axis of rotation of the idlerwheel will be in. one position. If it is then desired to shift the axisof rotation, it is necessary to loosen the nut 114 and move the U-shapedwasher angularly with respect to the shaft 113. When the axis has beenshifted the desired amount, the nut is re-tightened and the idler wheelwill then rotate on its new rotational axis. The idler plate has alsobeen provided with a pin 119 which extends therefrom and is carried bythe plate.

The flange 77 of the second air motor assembly 15 is provided with firstand second slotted openings 121 and a circular opening 122. A second airmotor 123 is provided and is secured to the flange of the second airmotor assembly by means of bolts 124 which extend through the slottedopenings 121 and into this air motor. A dowel pin 125 extends throughthe opening 122 and ,into the air motor 123. This construction has beenprovided so that the air motor 123 may be shifted angularly with respectto the cylindrical support member 12 and the split mounting collar 65for a purpose to be hereinafter described. The shifting of the air motor123 from one position to another has been illustrated in Figure 1 bymeans of the full line position and the dot-dash line position 126.Passageway means 129 (Figure 3) lead from the annular chamber 72 of thesecond air motor assembly and into the second air motor 123. Thisdescribed passageway means is the same as the construction of thepassageway means of the first air motor 80 which was describedhereinabove but not shown in the drawings. A second guard supportingpost 132 which is provided with a slot therethrough is fixedly securedto the split mounting collar of the second air motor assembly as at 133and extends therefrom. An eccentric nut member 134 is journalled forrotative movement on the guard supporting post 132. An angular movementplate 135 which is secured to the air motor 123 by bolts 136 is providedwith wall means 137 which surround the eccentric portion of the nutmember. Thus when the bolts 124 are loosened in the slotted openings121, the air motor 123 may be shifted angularly by rotating theeccentric nut member 134. When the air motor has been shifted thedesired amount, the bolts 124 are re-tightened and the air motor isagain fixedly locked in position. The split collar 65 of the second airmotor assembly is provided with an operating handle 109 which isintegrally formed therewith and which is similar to handle 88.

.As best shown in Figure 2, a guard 139 fits over the first guardsupporting post 90 and is secured thereon by means of a cotter pin 140whereas the opposite end portion resides within the slot in the secondguard supporting post.1 32. The ,pin 119 whichis carried by the idler,plateSiDds adapted to engage :the guard .139 and .keep [it intheposition shownin Figure 2.

Inroperation it maybe assumed for .the sake of ex ample that a newsanding belt is to be used by the machine. To put the sanding belt onthe machine, the handle 102 is moved from the first to the secondposition v(Figure 2) by depressing the spring biased detent 110 whichpermits travel of the handle and the idler wheel .100 to the dot-dashposition 108. The new belt is then placed over the pulleys of theair-motors and around the idler wheel. Thehandle 102 is then moved backto the first position. This properly tensions the sanding belt. Toacuate the device, air travels through the air supply line 63, through.the opening 60 of the swivel member 53, and from there through theopening 51 in the nipple 49 and into the chamber 42 (Figure 6). From thechamber 42, the air travels into the hollow cylindrical support memberand from there to either end thereof and into the respective air motors.This actnates the air motors and causes the sanding belt to rotate onthe pulleys. The sanding machine may be moved in two mutuallyperpendicular planes relative to the position shown in Figure 1 and themovement in the one plane is possible because of the construction of andcooperation between the swivel 125 member 53 and the nipple 49 (Figures6 and 7). The movement in the other mutually perpendicular plane ispossible because of the construction and cooperation of the supportmember 12 and the housing where the support member extends through thehousing 23 of the balancing. 130 assembly. The relative movement aboutthe axis of the cylindrical support member 12 has been shown in Figure3. If the sanding machine is in the position of the full line drawing ofFigure 3 while sanding a substantially horizontal surface, and it isdesired to sand 35 a vertical surface, it is only necessary to grasp thehandles and swing the device through 90 degrees. Movement in the otherplane can be accomplished in much the same manner. It is thus possibleto move the sanding machine to many positions without fouling the airsupply line 63 or any of the supporting lines. This can also be donewithout excessive fatigue to the workmen handling the device.

After the sanding belt has been in use for a period of time, the wear onthe same is in most instances not even across the entire width of thebelt. As a result, the belt will tend to track either toward the outsideor the inside of the pulley upon which it is riding. Depending uponwhere the wear has taken place on the belt, thus determining which waythe belt is tracking, the angular posi-C5 tion of the air motor of thesecond assembly is then shifted by loosening the bolts 124 and turningthe eccentric nut member 134 until the desired tracking is obtained andthen bolts 124 are re-tightened. To accomplish the desired tracking ofthe sanding belt on .the pulley of the Q first air motor, it isnecessary to shift the axis of rotation of the idler wheel 100. This isdone by loosening the nut "H4 and moving the U-shaped washer 115. Whenthe axis of rotation has been shifted to give the desired tracking, thenut 114 is tightened. It will be apparent Oii that at many times, thesanding of an object will not take place exactly on the pulley whichsupports the sanding belt but will take place at some point in between.Since the idler plate and hence the idler wheel, are held in theposition of Figure 2, only by the spring member (IQ 105, it will be seenthat if the belt is deformed centrally between the pulleys, the idlerwheel 100 will tend to float and thus compensate for this deformation.This maintains the sanding belt at a substantially constant tension.

It will thus be seen that the sanding machine of the (F1 presentinvention is capable of many angular positions relative to the verticaland horizontal without undue veflort and without fouling support and/orpower lines. The "tracking adjustments of the machine also provideforthe repositioning of the sanding belt when it becomes 5.5.

warm. The sander of the present invention is also desirable from thestandpoint that the cylindrical support member in addition to supportingthe air motors, serves as a manifold for distributing air under pressureto the motors for driving the same.

Although this invention has been described in its preferred .form with acertain degree-of particularity, it is understood that the presentdisclosure of the preferred form .-has been made only by way .ofexampleand that numerous changes in the details of construction and thecombination and arrangement of .parts may be resorted to withoutdeparting from the spirit and the scope of the invention as hereinafterclaimed:

What is claimed is:

1. A sanding machine including a hollow cylindrical member having firstand .second end portions and anin- .termediate portion, a supportingassembly comprising a housing surrounding said intermediate portion ofsaid cylindrical member, first and second lock collars secured to saidcylindrical member on either side of housing to prevent said supportingassembly from axial movement on said cylindrical member, shoulders onsaid lock collars and on said supporting assembly permitting apredetermined angular movement between said cylindrical member and saidsupportingassembly, wall means in said housing defining an annularchamber .between said housing and said intermediate portion of saidcylindrical member, said housing having a nipple extending generallynormal to the extent of said cylindrical member and having an openingtherein extending to and communicating vwith said annular chamber, aswivel member .fitting over said nipple and swivelably secured thereonby a screw extending into said nipple, said swivel member having anopening therein communicating with said opening .in said nipple,connection means interconnecting said opening of said swivel member withan air supply line, said connection means providing for relative angularmovement between said air supply line and said swivel member, first andsecond air motor assemblies secured to said first and second endportions of said cylindrical member respectively, said first air motorassembly comprising a first split mounting collar surrounding-said firstend portion of said cylindrical member .andfixedly secured thereto bymeans of a screw extending through said first collar and into saidcylindrical member and a screw extending between the ends of said firstsplit collar, Wall means in said first mounting collar defining a firstannular chamber between said collar and said first end portion of saidcylindrical member, said first end portion of said cylindrical memberhaving an opening communicating with said first annular chamber, saidfirst mounting collar having a flange thereon, said flange havingopenings extending therethrough, a first air motor, bolts extendingthrough said flange and into said first air motor for securing sametogether, passageway means leading from said first annular chamber intosaid first air motor, a first guard supporting post fixedly secured toand extending from said first mounting collar, a pivot collarsurrounding said guard supporting post, an idler plate carried by saidpivot collar, a pin carried by said idler plate, a lever arm connectedto said pivot collar for moving same about said guard supporting post,said lever arm movable between first and second positions, an idlerwheel mounted by said idler plate and comprising a shaft, a nut securingsaid shaft to said idler plate, a one-piece washer having opposedwedge-shaped surfaces residing on either side of said idler plate withsaid shaft extending therethrough, a first handle secured to said firstsplit collar opposite'said first air motor, a spring biased detentmounted by said first handle and normally engaging said lever arm tomaintain same in said first position, said second air motor assemblycomprising a second split mounting collar surrounding said second endportion of said cylindrical member and fixedly secured thereto by meansof a screw extending through said second collar and into saidcylindrical member and a screw extending between the ends of said secondsplit collar, wall means in said second mounting collar defining asecond annular chamber between said second collar and said second endportion of said cylindrical member, said second end portion of saidcylindrical member having an opening communicating with said secondannular chamber, said second mounting collar having a flange thereon,said flange having first and second slotted openings and a third openingextending therethrough, a second air motor, bolts extending through saidfirst and second slotted openings and a pivot member extending throughsaid third opening and into said second air motor for adjustablysecuring said second air motor, passageway means leading from saidsecond annular chamber into said second air motor, a second guardsupporting post fixedly secured to and extending from said secondcollar, an eccentric nut member iournalled for rotative movement on saidsecond guard supporting post, wall means extending from said second airmotor and surrounding said eccentric member, each of said first andsecond air motors including a pulley, said pulleys and said idler Wheeladapted to support and drive a sanding belt, and a guard mounted at oneend portion by said first guard supporting post and mounted at the otherend portion by said second guard supporting post with said idler platepin adapted to engage said guard at an intermediate portion.

2. A sanding machine including a tubular member having first and secondend portions and an intermediate portion, a balancing assembly mountingsaid intermediate portion of said tubular member for relative rotationof same with respect to said balancing assembly, means for securing saidbalancing assembly to an overhead support, air supply means, connectionmeans connecting said air supply means with said balancing assembly andproviding for relative angular movement of said connection meansrelative to said balancing assembly, passageway means providing for thepassage of air from said balancing assembly into said tubular member,first and second air motor assemblies fixedly mounted on said first andsecond end portions respectively of said tubular member, each said airmotor assemblies including an air motor having a pulley rotativelydriven by a drive shaft, each said air motor assemblies havingpassageway means providing for the passage of air to said first andsecond air motors respectively from said first and second end portionsof said tubular member respectively, said first air motor assemblymounting an idler plate for lateral movement with respect thereto, saididler plate having an idler wheel journalled for rotation thereon, meansfor adiusting the axis of rotation of said idler wheel, said pulleys ofsaid air motors and said idler wheel adapted to mount and drive asanding belt, means for adjusting said air motor of said second airmotor assembly for angular movement with respect to said air motor ofsaid first air motor assembly, and a sanding belt guard mounted by saidfirst and second air motor assemblies.

3. A sanding machine including a tubular member having first and secondend portions and an intermediate portion, a balancing assembly mountingsaid intermediate portion of said tubular member for relative rotationof same with respect to each other, air supply means, connection meansconnecting said air supply means with said balancing assembly andproviding for relative angular movement therebetween, passageway meansproviding for the passage of air from said balancing assembly into saidtubular member, first and second air motor assemblies fixedly mounted onsaid first and second end portions respectively of said tubular member,each said air motor assemblies including an air motor having a pulleyrotatively driven by a drive shaft, each said air motor assemblieshaving passageway means providing for the passage of air to said firstand second air motors respectively from said first and second endportion of said tubular member respectively, said first air motorassembly mounting an idler plate for lateral movement with respectthereto, said idler plate having an idler wheel journalled for rotationthereon, means for adjusting the axis of rotation of said idler wheel,said pulleys of said air motors and said idler wheel adapted to mountand drive a sanding belt, and means adjustably mounting said air motorof said second air motor assembly for angular movement with respect tosaid air motor of said first air motor assembly.

4. A sanding machine including a tubular member having first and secondend portions and an intermediate portion, a balancing assembly mountingsaid intermediate portion of said tubular member for relative rotationof same with respect to each other, air supply means, connection meansconnecting said air supply means with said balancing assembly andproviding for relative angular movement therebetween, passageway meansproviding for the passage of air from said balancing assembly into saidtubular member, first and second air motor assemblies mounted on saidfirst and second end portions respectively of said tubular member, eachsaid air motor assemblies including an air motor having a pulley, eachsaid air motor assemblies having pasageway means providing for thepassage of air to said first and second air motors respectively fromsaid first and second end portion of said tubular member respectively,said pulleys of said air motors adapted to mount and drive a sandingbelt, and means adjustably mounting said air motor of said second airmotor assembly for angular movement with respect to said air motor ofsaid first air motor assembly.

5. A sanding machine including a tubular member having first and secondend portions and an intermediate portion, a supporting assembly mountingsaid intermediate portion of said tubular member for relative movementof the same with respect to each other, air supply means, connectionmeans connecting said air supply means with said balancing assembly andproviding for relative angular movement therebetween, passageway meansproviding for the passage of air from said balancing assembly into saidtubular member, first and second air motor assemblies fixedly mounted onsaid first and second end portions respectively of said tubular member,each said air motor assemblies including an air motor having a pulley,each said air motor assemblies having passageway means providing for thepassage of air to said first and second air motors respectively fromsaid i rst and second end portion of said tubular member respectively,said first air motor assembly mounting an idler plate for lateralmovement with respect thereto, said idler plate having an idler wheeljournalled for rotation thereon, and means for adjusting the axis ofrotation of said idler wheel, said pulleys of said air motors and saididler wheel adapted to mount and drive a sanding belt.

6. A mechanism for driving an abrading member including a tubularmanifold, first and second air motors secured to opposed end portions ofsaid manifold, means for supporting said manifold, an air supplyconduit, connection means for supplying air from said air supply conduitto an intermediate portion of said manifold, said connection meanspermitting movement of said motors in two mutually perpendicular planesrelative to said air supply conduit, passageway means supplying air fromsaid manifold into said air motors, means for shifting said second airmotor angularly with respect to said manifold, an idler wheel forengaging the abrading member, and means for shifting the axis ofrotation of said idler wheel.

7. A mechanism for driving an abrading member in- 'cluding a secondmember having air passageway means her, passageway means supplying airfrom said air passageway means of said second member into said airmotors, and means for shifting said second air motor angularly withrespect to said second member.

8. A mechanism for driving an abrading member including a supportmanifold, first and second air motors secured to opposed end portions ofsaid support manifold, an air supply means, connection means forsupplying air from said air supply means to said support manifold, saidconnection means permitting movement of said motors relative to said airsupply means, passageway means supplying .air from said manifold to saidair motors, and

means for shifting said second air motor with respect to said manifold.

References Cited in the file of this patent UNITED STATES PATENTS871,323 Clemons Nov. 19, 1907 927,066 Oakley July 6, 1909 2,431,795Elmes Dec. 2, 1947 2,449,519 Sutton Sept. 14, 1948 2,463,278 KruegerMar. 1, 1949 2,507,677 Packer et a1. May 16, 1950 2,561,589 Newton July24, 1951

